Externally ignited internal combustion engine

ABSTRACT

An internal combustion engine in which each cylinder or combustion volume includes a separate ignition chamber which communicates with the main combustion chamber through a relatively narrow channel or channels. The combustible mixture is delivered to the separate chamber exclusively through these channels by the compressive action of the piston and is ignited there by a suitable electrical spark, for example. There is no additional admission of fuel or fuel mixture to the separate ignition chamber. The channel or channels terminate in the ignition chamber in such a manner, for example, tangentially, that one or more vortices are generated in the chamber prior to ignition. The channels are so oriented that the emerging igniter flames are directed to potential hot cells in the main combustion chamber where auto-ignition could occur.

This is a division of application Ser. No. 688,051, filed May 19, 1976now abandoned.

BACKGROUND OF THE INVENTION

The invention relates to an externally ignited internal combustionengine of the type which includes a main combustion chamber and aseparate ignition chamber in which the spark plug is located. The maincombustion chamber and the ignition chamber communicate through achannel which terminates in the ignition chamber substantiallytangentially.

Due to the presence of the ignition chamber, even very lean fuel-airmixtures can still be ignited in the main combustion chamber. The reasonfor the favorable ignition properties is due to the fact that, insteadof having a single electric spark, such as is present in ordinaryinternal combustion engines, the ignition in the main combustion chamberis initiated by a torch-like jet which bursts out of the ignitionchamber. It is this jet which permits a uniform reaction of the chargeeven when the mixtures used are very lean. The mixture prevailing in theignition chamber is ignited in known manner by means of a spark plug. Ina known process, the ignition chamber is supplied with a substantiallyricher mixture than that supplied to the main combustion chamber which,in turn, is created by supplying supplementary fuel. In these so-called"stratified charge" engines, any faulty mixture preparation (for exampledue to soot deposition in the injection valve) may cause excessiveenrichment in the region of the spark plug and thus cause ignitionfailure or incomplete combustion which, in turn, would lead to adeterioration of the power and the purity of the exhaust gases of theengine. These problems which occur in stratified charge engines aremagnified because the tangential influx causes centrifugal forces whichhave an effect especially on the heavier fuel drops in the fuel-airmixture. The same is true for rotary piston engines although, in rotarypiston engines, the main combustion chamber rotates at the same rate asthe piston.

In order to counteract these above-mentioned difficulties, it has beenproposed in a known internal combustion engine of this type to disposethe spark plug in a separate chamber, immediately adjacent to theignition chamber, into which the enriched mixture flows from theignition chamber through channels to be ignited. In this last process,there is a danger of the deposition of soot in the very narrow channelsas between ignition chamber and separate chamber. Furthermore, no swirlor vortex is created in the ignition chamber so that the reactionvelocity of the charge in the ignition chamber is lower than in a swirlchamber design, which again brings disadvantageous characteristics ofthe energetic reactions in the main charge.

Furthermore, stratifications of the charge of the type described aboveentail a substantially increased cost because they require a directinjection system with the corresponding requirement for timing the fuelinjection, the ignition and correlating these times with the overalltiming of the engine.

Also known are engines with an ignition chamber in which very highcompression and a high turbulence of a substantial portion of the totalcharge is supposed to provide the very maximum power. However, theseengines exhibit very rough running and relatively unfavorable exhaustgas characteristics. The high compression in the main combustion chamberresults in a high mixture temperature which creates so-called hot cells,i.e, regions of especially elevated temperature, so that, in theselocations, there is the possibility of auto-ignition of the fuel-airmixture. By creating a rotational motion in the main combustion chamber,such auto-ignition is counteracted but, again, rotational motion coupledwith high compression in the main charge leads to a rough-running engineand, furthermore, such a mixture is harder to ignite because it containsvortices of large diameter. Thus, the ignitability, the exhaust gasrequirements, the smooth running of the engine, small dead space, power,fuel consumption, etc., all make certain demands on the design and areof such complicated and partially contradictory nature that an optimumcompromise among all these requirements is very difficult.

OBJECT AND SUMMARY OF THE INVENTION

It is a principal object of the invention to provide an internalcombustion engine of the general type described above which permitsseparate optimization of the processes taking place in the ignitionchamber and the main combustion chamber, respectively. The inventionprovides that the ignition chamber and the main combustion chamber areseparated so that the ignition of the mixture takes place independentlyin the two chambers. Finally, the invention provides that the influenceof events in the ignition chamber on processes taking place in the maincombustion chamber is especially to cause a uniform and rapid reactionof the main charge.

These objects are attained according to the invention by providing thatthe fuel-air mixture which is intended for ignition flows into theignition chamber from the main combustion chamber exclusively through achannel terminating in the ignition chamber tangentially. The deliveryof the charge through the tangential channel creates a cylindricalvortex or a potential vortex and results in a homogeneous admixture ofair and fuel without supplementary fuel injection. The displacement ofthe ignition chamber with respect to the main combustion chamber and thetangential entry of the charge into the ignition chamber causesformation therein of a so-called solid vortex which gradually undergoestransition into a potential vortex which guarantees a homogeneousadmixture of air and fuel. It is significant that the homogeneity offuel thus attained is not subsequently disturbed by injectingsupplementary fuel as would be the case in a stratified charge engine.In the region of the boundary layer, the speed of the mixture in thevortex is relatively low and thus particularly small turbulentfluctuations are created, i.e., the linear dimensions of localturbulences are very small. Furthermore, the overall favorablehomogeneity of the charge is affected slightly by centrifugal forceswhich might somewhat enrich the mixture in the region of the boundarylayer at the wall. Since the electrodes of the spark plug are locatedwithin this wall boundary layer, the conditions for ignition of evenvery lean fuel-air mixtures are favorable. Since the entire ignitionprocess takes place in the ignition chamber, and is separate from anyprocesses in the main combustion chamber, the latter may be shaped inany desired and optimum manner without being affected by events in theignition chamber. For this reason, it is possible to ignite mixtureswhose air number λ is of the order of 1.6 whereas, conventionally, thelimit of ignition is λ=1.3. The main reason that very lean mixtures arenormally difficult or impossible to ignite is due to their inhomogeneityas well as to the high velocity and large vortex size in the region ofthe spark plug.

In a favorable embodiment of the invention, the ratio of the volume ofthe main combustion chamber at the end of the compression stroke to thevolume of the ignition chamber is greater than 5 and preferably between10 and 25. The relatively small volume of the ignition chamber resultsin several decisive advantages. Firstly, due to the relatively lowsurface area, the frictional and thermal losses are small as is thetendency for hydrocarbon emissions. For the same reason, the firingchannel between the ignition chamber and the main combustion chamber isalso kept very short. The length of the channel is limited by criteriaincluding the materials used and the necessity to eliminate glowignition at relatively hot points of the channel. Furthermore, theignition extends over a relatively short length of time when theignition chamber is small so that the so-called ignition delay for themain charge is also kept small and this is very favorable, especially athigh engine rpm, inasmuch as the compressed main mixture is ignitedsubstantially from its edge regions. If the apparatus according to theinvention is used in rotary piston engines, the flame emerging from theignition chamber extends over the main combustion chamber long enough toinsure a rapid and reliable combustion of the main charge. Since therotation of the charge in a small ignition chamber is smaller than wouldbe the case in a large one, thermal losses at the wall are also reducedand, furthermore, the initial pressure increase at the onset of ignitionis smaller, which makes the engine operation smoother and results in areduced mechanical stress of the involved parts of the engine. Thesmaller the ignition chamber, the smaller is the size of the potentialvortex created therein which, in turn, is made up of a large number ofsmaller vortices, so-called dispersion vortices, whose dimensions areproportional to the main or potential vortex. The ignitability of thevortices depends on their size and the smaller and more minute they are,the more homogeneous is the mixture and the easier it is to ignite it.When regarded from the viewpoint of matter and momentum exchange, theflows prevailing in a small ignition chamber are more orderly,especially in the region of the wall, where very small vortices prevail,resulting in more favorable ignitability than would be the case in alarger ignition chamber. All these observations are important adjunctsof the invention.

In one additional embodiment of the invention, the ratio of theprojections of the cross section of the channel to that of the ignitionchamber is 0.1 to 0.4, and preferably 0.15 to 0.3. When the ratio is ofthis order of magnitude, a sufficient decoupling of the ignition chamberfrom the main combustion chamber is guaranteed and any disadvantageousinfluence of the two chambers on each other is thereby avoided.

In accordance with an embodiment of the invention which is not confinedto the internal combustion engine as described but may also be used,e.g. in stratified charge engines, the central portion of the ignitionchamber contains a core which extends from one wall to the other. Sincethe translational motions of particles in a vortex are very small in thecenter, the danger of auto-ignition would be highest there. The coreprevents this danger, especially for ignition chambers which aredisc-shaped.

Another embodiment of the invention, also not limited to enginespreviously described, includes additional bores or channels which leadfrom the ignition chamber to locations within the main combustionchamber that are thought to be potential hot cells. These hot cells areoften the cause of detonation or pinging. By providing the additionalbores aimed at potential hot cells, the charge in those locations iscombusted early and results in a controlled behavior of the entireignition process.

Yet another embodiment of the invention, which is not confined only toapplication in engines of the type described here, provides that severalchannels between the ignition chamber and the main combustion chamberare so arranged that two separate vortices of opposing direction ofrotation are formed within the ignition chamber. The border regionbetween the two vortices will thus acquire a particularly high degree ofturbulence and flame velocity due to the very high velocity gradientbetween the two vortices at this point. The very rapid reaction in thecharge, which is very favorable especially for stratified chargeengines, results in relatively late ignition times which are favorablefor optimum power and which represent a good approximation to theso-called constant volume combustion process and thus provides thecombustion with a tendency to avoid detonation. The geometricalconditions of such an ignition chamber are also favorable because theypermit separate direction of the flaming jet into the combustion chambersince each vortex is associated with a separate firing channel leadingin opposite directions.

In yet another embodiment of the invention, the upper edge of theelectrode of the spark plug lies within the boundary layer of the wallof the ignition chamber and approximately opposite the termination ofthe connection channel in the ignition chamber. If the ignition chamberincludes multiple vortices, the main electrode of the plug may be madeappropriately long, or several locations for ignition are provided.Inasmuch as the combusted gases tend to flow to the center of theignition chamber after ignition has taken place, uncombusted mixture ispulled past the spark plug and thus a particularly favorable completeignition of the entire mixture takes place. The core of the flameremains associated with the plug and this has a favorable effect on thestability of the initiation of ignition and on the speed of thereaction. When vortices of opposite rotation are present, the velocitygradient is very high both between the vortices as well as in the wallboundary layer and this is also favorable for the initiation ofignition. When the invention is used, the ignition delay (the timebetween the occurrence of the spark and the propagation of the flamefront) is much lower than usual and, due to the very intense vortexmotion of the charge, the reaction time in an ignition chamber having adouble vortex is much higher than in customary ignition chamber systems.Due to the very abrupt increase of the pressure, the combustion processcomes close to being an ideal process, i.e., the constant volume processof the theoretical Otto engine. Yet another advantage is that the pointof ignition most favorable for optimum power is independent of rpm andof load or induction tube pressure.

Since the charge exchange in the turbulence chamber is orderly andapproximately proportional to rpm, the ignition and combustion in themain combustion chamber is also favorable because the flame shooting outof the turbulence chamber has a positive influence on the maincombustion chamber processes but does not require that the maincombustion chamber be made especially suitable due to the requirementsof ignition. This is especially true for rotary piston engines.Therefore, the cyclic fluctuations of combustion are very low even whena lean mixture is burned in the two combustion chambers. The tendency ofthe motor to knock under full load is also substantially reduced. Whenseveral connection channels are present, the combustion process in themain combustion chamber is similar to multiple ignition which increasesthe reaction rate of the charge in the main combustion chamber and thusfavorably influences the efficiency. The use of the invention instratified charge engines results in substantial advantages, yet theunfavorably high emission of hydrocarbons of such engines which isnormally encountered is not found when the invention is used therein dueto the especially homogeneous charge provided by the invention. Similaradvantages are obtained with respect to the emission of nitrogen oxidesbecause the partial admixture of rich and lean mixtures in ordinarystratified charge engines is avoided so that somewhathyperstoichiometric compositions whose combustion would lead to veryhigh concentrations of nitrogen oxides are avoided.

The invention will be better understood as well as further objects andadvantages thereof become more apparent from the ensuing detailedspecification of a number of preferred embodiments taken in conjunctionwith the drawing.

BRIEF DESCRIPTION OF THE DRAWING

FIGS. 1, 2, 11, 12, 13 and 14 depict different preferred embodiments ofignition chambers according to the invention;

FIGS. 3-10 depict different dispositions of the connection channel andof the ignition means; and

FIGS. 15 and 16 are illustrations of the use of the ignition chamber ina rotary piston engine.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning now to FIGS. 1 and 2, there are shown sections of an internalcombustion engine which illustrate one possible location of theapparatus according to the invention. An engine cylinder 1 has a piston2 whose top 3 defines the main combustion chamber 4. A relatively leanfuel-air mixture is admitted during the suction stroke of the piston 2into the main combustion chamber 4 through the induction tube 5 and theinlet valve 6. The fuel preparation means are not shown in eitherfigure.

When the piston 2 moves during its compression stroke, a portion of thislean fuel-air mixture flows through a connection channel 7 into anignition chamber 8. The terminus of the connection channel 7 in theignition chamber 8 is tangential thereto so that an orderly vortex flowis formed in the ignition chamber 8. The boundary layer of the fuel-airmixture in the vicinity of the wall 9 engages the electrode 10 of aspark plug 11 where it is ignited. Due to the low speed of the boundarylayer and due to the very homogeneous admixture of the fuel-air mixtureand any residual gases, even very lean mixtures are capable of beingignited. The relatively small volume of the ignition chamber 8 insuresthat the dispersion vortices, i.e., the constituent swirls which formthe main vortex, are very small and thus favor ignition. Due to thecharacteristics of the potential vortex which is generated, any hot,i.e., ignited, fuel-air components, migrate to the center of theignition chamber so that unignited constituents flow toward the ignitionchamber wall and thus enter the region of the electrode 10. The flowfollows a spiral path, as indicated by arrows, from the spark plug tothe center of the chamber. Even after the electrical spark has expired,ignition continues to take place because of the so-calledflame-retaining effect at the point of ignition. Ignition also takesplace due to the spirally propagating flame by convection withuncombusted gas. Shortly after the ignition of the mixture in theignition chamber, the flame shooting through the connection channel 7causes ignition of the similarly lean fuel-air mixture in the maincombustion chamber 4. Because of the very intense flaming jet emergingfrom the connection channel 7, even very lean mixtures up to an airnumber λ=1.6 are still ignitable (air number proportional to the ratioair/fuel). In order to obtain the advantages described above, it isnecessary to make the volume of the ignition chamber as small aspossible compared to the residual volume of the main combustion chamberat top dead center. The ratio of the combustion chamber volume to thatof the ignition chamber should be higher than 5 and a value of 10 to 20has been shown to be especially favorable. The shape of the ignitionchamber could be spherical, cylindrical or, as shown in FIG. 1,bell-shaped, including a flat face portion 12 interrupted by theconnection channel 7. The presence of the flat surface results in areduction of the vortex speed in the vicinity of the spark plug whichfavors the ignition onset due to the creation of a homogeneous mixture.

In order to obtain a high exit velocity of the hot gases from theignition chamber into the main combustion chamber, it is suitable toslightly enlarge the connection channel 7 in the direction of the maincombustion chamber. This construction is shown in FIG. 1 and when theconnection channel is embodied in this manner, somewhat as a kind ofLaval nozzle, the speed of the gas may exceed the speed of sound forhigh rpm.

The vortex which is generated in the ignition chamber exhibits arelatively small gas motion in the center so that the possibility ofauto-ignition is high in the center of the vortex, especially for highcompression ratios. Auto-ignition is undesirable because the onset ofignition is unpredictable. In order to prevent auto-ignition, theexemplary embodiment shown in FIG. 1 exhibits a material core 18disposed in the center of the ignition chamber, and extending from onewall to the other coaxially with the axis of rotation of the vortex. Acentral core 18 of this type, which prevents auto-ignition, is anadvantage not only in the ignition chamber of the invention, but quiteuniversally for any type of ignition or swirl chamber, even for thoseused with stratified charge engines. The material center 18 is also veryadvantageous when the swirl chamber has the shape of a disc.

The second preferred exemplary embodiment shown in FIG. 2 is differentfrom that shown in FIG. 1 principally by including an insert composed ofparts 13 and 14. The part 13 is a threaded member which is intended toclamp the part 14 within the cylinder head 3. The part 14 includes theconnection channel 7 which creates a communication between the maincombustion chamber 4 and the swirl chamber 8 and the part 13 is adaptedto hold the spark plug 11. Both part 13, as well as the spark plug 11,are accessible from outside of the engine. A lock nut 15 preventsloosening of the part 13 and a copper gas seal 16 may also be provided.This embodiment may be altered by welding the parts 13 and 14 togetherpermanently, in which case the screw threads on the part 13 would extendcompletely down to the combustion chamber 4. In such a case, an externalmark would indicate the orientation of the injection channel 7 withrespect to the main combustion chamber 4.

It is known that, in places of gas transition between the combustionchamber 4 and the cylinder head 3, so-called hot cells may be formed.These are places in which the motion of the mixture is relatively slow,for example dead corners, and these places may be sources ofauto-ignition which leads to fuel detonation and pinging. As illustratedin FIG. 2, hot cells may be made ineffective by the provision ofadditional channels 17. On the one hand, these additional channels 17generate a more vigorous motion of the fuel-air mixture in the deadspots and, secondly, the mixture in these places is now ignited by aflare aimed at them through the additional channels 17. Such additionalchannels may be used not only in internal combustion engines of the typedescribed here, but in any internal combustion engines which includeignition or swirl chambers, even stratified charge engines.

FIGS. 3, 4 and 5 are diagrams illustrating in enlarged manner a part 14and the two connection channels 7' contained therein. In FIG. 3 the viewis as seen from the main combustion chamber 4, FIG. 4 is a verticalcross section through the part 14, while FIG. 5 is a view from theignition chamber 8. The angle between the central axes of the twochannels 7' is preferably approximately 90°. By using two connectionchannels 7', appropriately disposed, the favorable ignition conditionsin the ignition chamber 8 in the region of the spark plug are maintainedbut, in addition, the ignition process in the main combustion chamber issubstantially improved because the two igniter jets now providedtogether envelop a relatively large area of the main combustion chamberso that the reaction rate in the charge is substantially increased. Thisrapidity of combustion reduces the tendency of the motor to exhibitdetonation so that very lean fuel-air mixtures are still ignitable and avery favorable condition for the emission of NOx components and the fuelconsumption is obtainable.

In the exemplary embodiment shown in FIG. 6, the connecting bridgebetween the two connection channels 7' is omitted so that the now singlechannel 7" has a crescent-like cross section. FIG. 6 is a vertical crosssection of the same type as shown in FIG. 4.

An embodiment with a single channel 7" may be preferable, especially forhigh performance engines, because the absence of the bridge prevents theformation of hot cells.

FIGS. 7-10 illustrate ignition chambers in which two connection channelsare so arranged as to produce two adjacent vortices having the same axisof rotation. The exemplary embodiment shown in FIGS. 7 and 8 exhibits acylindrical ignition chamber in which two mutually parallel channels7''' terminate tangentially. Each of the channels 7''' lies adjacent oneend face of the ignition chamber so that two cylindrical swirls arecreated which rotate adjacent to one another, as may be seen from FIG.8, where the plane of the swirls is indicated by arrows. Since thedirection of motion is opposite in the two swirls, the border regionbetween the two swirls exhibits very high turbulence with very finemicro-vortices and thus will generate a very high flame velocity. Thisincrease of the flame or reaction speed is due to the extremely largevelocity gradient existing between the two swirls which also favors anddefines the turbulent magnitudes of the transfer of mass, momentum andheat. The rapid reaction in the charge permits late ignition timeswhich, in turn, favor maximum power, so that a good approximation to theso-called constant volume combustion process is possible and the enginedoes not tend to ping. The geometry of the ignition chamber justdescribed permits an optimum direction of the ignition flames guidedfrom the ignition chamber into the main combustion chamber. If required,the two channels 7''' may cross, as shown in FIG. 9, or they may be in amutually V-shaped configuration as shown in FIG. 10. It will beunderstood that an embodiment in which two mutually oppositely rotatingvortices are created in a single ignition chamber is not limited tointernal combustion engines using a homogeneous charge flow, but isapplicable in general to any ignition chamber, in particular thoseemploying stratified charge, and Diesel engines.

In order to improve the ignition of the fuel-air mixture in the ignitionchamber, the ignition chamber 8 may be thermally insulated from thecylinder head 3 by an air space 19, as shown in FIG. 7. It is especiallyfavorable if the air space 19 is located at the sides of the ignitionchamber 8, especially the sides which are passed by the uncombustedfuel-air gas on its way to the spark plug. Any other thermal insulatormay also serve the same purpose.

As illustrated in FIGS. 7 and 8, the primary ignition may take place bymeans of a single spark plug having a single electrode 20 while the wallof the ignition chamber is the second and ground electrode of the plug.If the main electrode 20 is extended appropriately as shown in FIG. 8,both swirls may be ignited simultaneously. By this embodiment of thespark plug, in which the ground electrode is provided by the walls ofthe ignition chamber, the spark is forced to traverse the entirefuel-air mixture in the chamber and terminates in the boundary layer atthe wall where ignition is particularly favorable.

The ignition process can be further improved by a kind of pre-ionizationwith the aid of two ignition units 21 disposed in series in thedirection of flow of the mixture as illustrated in FIG. 13. Ignition maybe initiated simultaneously at both electrodes, or in sequence.

A similar effect may be obtained by using an ignition system having arelatively long duration of ignition and high energy, so that anyparticles which have been ionized or activated return to the area of theelectrodes, after having traveled in the vortex, at a time when theelectric spark is still present there. It has also been found to beadvantageous if the effective surface of the ignition chamber has acatalytic effect on the combustion. This may be done, for example bymanufacturing the insert from the element Nickel.

The connection channels 7, 7', 7", and 7''' have preferably a circularor elliptical cross section. If the ignition chamber exhibits only asingle main vortex, and if the cross section of the connection channelis elliptical, it is important that the major axis of the ellipse beparallel to the rotational axis of the vortex. It has been shown to beadvantageous in principle if the ratio of the overall cross section ofthe connection channel or channels to the cross section of the ignitionchamber is of the order of 0.1 to 0.4 and preferably 0.15 to 0.3. Thischange in cross section represents a clear offset of the ignitionchamber from the main combustion chamber without having a detrimentaleffect on the ignition. Preferably, the electrodes 10, 21 of the sparkplug 11 are located approximately opposite the point of injection from asingle channel or opposite the center of the entry points of severalchannels. Since it is desirable that the electrical ignition process bewell within the boundary layer of the vortex at the wall, the centerelectrode of the spark plug should extend only a few tenths of amillimeter into the ignition chamber unless, as described above, thewall of the ignition chamber itself provides the ground electrode of thespark plug. When the ignition chamber includes oppositely rotatingvortices, and if the ignition process is generally confined to thecentral plane between the two vortices, the center electrode may thenextend further into the ignition chamber without any disadvantageouseffects because the flow in this case has the general character ofboundary layer flow. The principal condition for all these cases is thatthe point of ignition is a place where the gases exhibit orderly flow oflow velocity and very finely grained turbulence, which results in aminimum ignition delay and a minimum of dispersion of the ignition time.Furthermore, in such a disposition, after ignition has begun, the flameis retained near the spark plug for a certain length of time so thatfresh portions of the charge may still be ignited even though theelectrical spark is no longer present. Due to the favorable orderlyignition in the ignition chamber, the velocity of the flaming jet in theconnection channel 7 may be approximately proportional to the rpm sothat the charge reaction in the main combustion chamber can also takeplace in an approximately rpm-synchronous manner. For this reason, themost favorable timing angles are substantially unaffected by changes inload and rpm. Furthermore, when oppositely rotating vortices are used,the tendency to auto-ignition is much reduced, due to the very highturbulence in the region of contact. When fuel is deposited on the wall,the turbulence causes very favorable vaporization and atomization of thefuel. The very good admixture of air and fuel in a counter-rotating flowis also favorable. Finally, the appropriate disposition of theconnection channels causes a very large region of the main combustionchamber to be accessible to the ignition jet and thus leads to a rapidcombustion of the charge.

FIGS. 11 and 12 illustrate an example in which the compression chamber 4is hemispherical and in which the ignition chamber insert 13 partiallyenters the combustion chamber 4. In order to permit the igniter jets tocover a large portion of the volume of the main combustion chamber, thisexample provides three channels 7"" which terminate tangentially in theignition chamber 8' but otherwise extend substantially radially withrespect to the axis of the insert. In the examples shown in FIGS. 13 and14, the insert 13 which includes the ignition chamber 8 is coupled tothe cylinder head 3 by a bayonet lock 24 and is secured with a screw 25.This example further shows how the separation of the ignition chamber 8from the main combustion chamber 4 permits a separate optimizationprocess. The favorable homogenization of the fuel-air mixture isobtained by creating a vortex flow in the main combustion chamberindicated by the arrow and of a type suitable for the requirements ofthe combustion chamber. In some combustion chambers it may beadvantageous if the vortex is generated in the induction tube or at theinlet valve and then enters the combustion chamber 4. In other engines,the vortex may only be generated by a suitable shaping of the combustionchamber. In any case, the fuel preparation in the main combustionchamber may take place independently of anything done in the ignitionchamber 8, according to the invention. By providing a fully homogenizedfuel-air mixture, moving in orderly manner in the main combustionchamber, and by also providing the above-described embodiments of theignition chamber 8, which represent independent optimization of theconditions of ignition within the ignition chamber 8, an overalloptimized engine operation can be achieved.

The adaptation of the ignition chamber to the main combustion chambermay include forming the connection channel or channels in such a waythat the mean direction of the flow out of these channels is guided tothe region of the exhaust valve of the engine. In this manner, thedetonation usually initiated in that region may be suppressed.

The ignition chamber according to the invention may also be used forrotary piston engines.

In FIGS. 15 and 16, there are illustrated preferred embodiments of theinvention in a rotary piston engine including the rotary piston 27. Inboth figures, the rotary piston 27 is shown in the position in whichignition has just started in the ignition chamber, i.e., slightly beforethe compression chamber reaches its smallest volume. Prior to achievingthis position, the ignition chamber 8 is connected to the combustionchamber 28 by the rotating piston 27 so that the motion of the charge inthe rotating main combustion chamber carries the lean mixture throughthe channel 7 into the ignition chamber 8.

At the moment of the ignition, in the exemplary embodiment of FIG. 15,the channel 7 is obliquely opposite to the long extent of the combustionchamber 28. Accordingly, the gases emerging from the ignition chambermix intimately with the main charge in the combustion chamber and theigniting jet covers the charge. Both of these features result in afavorable rapid and uniform reaction in the mixture in the maincombustion chamber.

The exemplary embodiment shown in FIG. 16 exhibits several channels 7'''which are provided to obtain a multiple ignition, which is especiallyfavorable in a rotary piston engine which has inherently unfavorablecombustion chamber geometry and unfavorable charge motion.

The foregoing represents preferred exemplary embodiments of theinvention and it will be understood that numerous other embodiments andvariants thereof are possible within the spirit and scope of theinvention, the latter being defined by the appended claims.

What is claimed is:
 1. In an internal combustion engine which includes ahousing, means in said housing defining a main combustion chamber, meansfor generating a combustible vapor mixture and means for admitting saidcombustible vapor mixture to said main combustion chamber, theimprovement comprising: an ignition chamber defined within said housingand having an arcuately shaped side wall, said ignition chamber beingdisposed separate from said main combustion chamber and communicatingtherefrom through two oppositely disposed channels arranged tangentiallywith respect to said arcuately shaped side wall which terminate in saidignition chamber in such a manner that the flow of combustible vaporfrom said main combustion chamber into said ignition chamber generatestherein two vortices rotating in opposite directions; said maincombustion chamber having a minimum volume at the top of the compressioncycle which is at least 5 times as great and preferably 10 to 25 timesas great as the volume of said ignition chamber; said channels having aflow cross section of between 0.1 to 0.4 and preferably between 0.15 to0.3 of the cross-sectional area of said ignition chamber; whereby thepassage of said vapor mixture into said ignition chamber along saidignition chamber side wall creates therein a vortex flow of homogeneousvapor without supplementary fuel admission to said chamber and withoutcharge stratification.
 2. An internal combustion engine as defined byclaim 1, wherein said ignition chamber is substantially cylindrical. 3.An internal combustion engine as defined by claim 1, wherein saidchannel is aimed in the direction of an exhaust valve of said internalcombustion engine.
 4. An internal combustion engine as defined by claim1, wherein said two channels are parallel.
 5. An internal combustionengine as defined by claim 1, wherein the axes of said channels lie indifferent planes.
 6. An internal combustion engine as defined in claim1, wherein said ignition chamber includes electric ignition meanslocated substantially diametrically opposite from and medially of thetermini of said at least two channels in said ignition chamber, andwherein the center electrode of said electric ignition means does notextend beyond the wall boundary layer of said fuel mixture vortex.
 7. Aninternal combustion engine as defined by claim 1, wherein the surface ofsaid ignition chamber is catalytically effective.
 8. An internalcombustion engine as defined by claim 1, wherein said ignition chamberis at least partially insulated thermally from said housing.
 9. Aninternal combustion engine as defined by claim 1, further comprisinghigh energy ignition means with an ignition energy of at least 100 mJper ignition and a duration of ignition of at least 0.5 milliseconds forpre-ionization of gases and subsequent combustion of gases after atleast one passage around said vortex.
 10. An internal combustion engineas defined in claim 1, wherein said ignition chamber includes electricignition means located substantially diametrically opposite from andmedially of the termini of said at least two channels in said ignitionchamber, and wherein one of the electrodes of said electric ignitionmeans is the wall of said ignition chamber.
 11. An internal combustionengine as defined by claim 10, wherein the major dimension of the otherof said electrodes is substantially parallel to a wall of said ignitionchamber and is substantially transverse to the direction of flow of saidvapor in said vortex.
 12. An internal combustion engine as defined byclaim 8, further comprising a separate housing for said ignitionchamber, said separate housing being thermally insulated from saidengine by air spaces.
 13. An internal combustion engine as defined byclaim 12, including means for thermally insulating the wall of saidignition chamber lying ahead of said electric ignition means as seen inthe direction of flow of mixture in said vortex.